Titanium alloy ingot phase transition point detection method

Abstract

The present application relates to titanium alloy phase transition point detection technical field, disclose a kind of titanium alloy ingot phase transition point detection method, comprising the following steps, step one, high-temperature solid solution, in ingot riser sampling obtains multiple test samples, all test samples are heated to T β +(10-300) ℃, after heat preservation, extremely fast cooling;Step two, low-temperature aging, after cooling all test samples in step one in T β -(200-400) below heat preservation, then heated to T β -(30-60) ℃, after heat preservation, cooling;Step three, phase transition point detection heat treatment, after cooling all test samples in step two are divided into multiple groups, multiple test samples are simultaneously heat treated, the number of heat treatment temperature value is equal to the number of test sample group, all heat treatment temperature value is gradient distribution with T β As center and equal difference value;Step four, phase transition point detection, according to high-magnification structure content evaluation phase transition point.The present application patent solves the problem that titanium alloy phase transition point detection process in prior art is complex and detection precision is poor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium alloy phase transition point detection, and particularly relates to a titanium alloy ingot phase transition point detection method. BACKGROUND

[0002] Titanium alloy has high specific strength, good ductility and good fracture toughness, and its market share in the field of aerospace is increasing. High-end titanium alloy materials for aerospace are usually forged at (T β -50℃) to (T β +30℃) to obtain superior performance. Within this narrow range, especially near the phase transition point, the microstructure of titanium alloy changes significantly with temperature, resulting in completely different results in product performance. In particular, such changes are generally irreversible. In actual production, there are large differences in phase transition points among titanium alloys of the same grade, so it is necessary to evaluate the phase transition point of each batch of titanium alloy materials for the production and application of titanium alloy.

[0003] In the current detection method, the conventional detection method is to evaluate the phase transition point by the content of alpha phase. Specifically, according to the phase transition process of titanium alloy, the content of alpha phase is less and less as it approaches the phase transition point. Therefore, in the detection process, only the samples are heated (the samples are in multiple parts during the heating process, and temperature values equal to the number of samples are set near the empirical T β in the heating process, and the temperature values are distributed in a gradient around the empirical T β ), and then the samples are rapidly cooled by water cooling (the phase content in the titanium alloy does not change during the rapid cooling process), and finally the content of alpha phase in different samples is detected. When the content of alpha phase is less than the specified value of 3%, the heating temperature value corresponding to the sample is the phase transition point value of the titanium alloy. Ideally, the detection of titanium alloy phase transition point at the ingot stage is the fastest and most economical, and the newly smelted titanium alloy ingot is all beta phase. Although the existing method can detect the phase transition point value of titanium alloy, there are still problems such as complex process, difficulty in distinguishing residual lamellar alpha phase, martensite and twin crystal, and poor detection accuracy in the actual detection process. SUMMARY

[0004] The present application aims to provide a titanium alloy ingot phase transition point detection method to solve the problem of complex process and poor detection accuracy in the detection of titanium alloy phase transition point in the prior art.

[0005] The inventors found in actual detection process that when the phase transition point of titanium alloy is detected by using the existing conventional technology, when the ingot is heated to precipitate alpha phase, due to the existence of semi-coherent interface between alpha phase and beta phase, only long and thin lamellar alpha phase can be precipitated, the length of alpha phase is very long but the thickness is very small when the phase transition point is approached, and when subsequent water cooling is performed at high speed, lamellar supercooled martensite is also precipitated in the titanium alloy, which has similar morphology to the lamellar alpha phase and is difficult to distinguish, so the alpha phase content is difficult to evaluate under an optical microscope, and finally the detection accuracy of the phase transition point of titanium alloy is poor.

[0006] In order to solve the above problems, multiple forging is usually performed before detection in the prior art, so as to break the semi-coherent interface between alpha phase and beta phase, and finally equiaxed or short rod-shaped alpha phase is precipitated in the equilibrium state, so that the morphology of alpha phase is distinguished from supercooled martensite, the detection of alpha phase is facilitated, and the detection accuracy is improved. The inventors found that although the multiple forging can more clearly detect alpha phase, in actual operation process, the temperature value between the actual phase transition point of the ingot and the experienced phase transition point may have a large difference, and the internal organization of the titanium alloy may be deteriorated during the multiple forging, and then a large amount of time and material cost is wasted to perform remedial forging on the blank to recover the loss, so that the cost and complexity of detection are increased, which is not conducive to quickly and accurately detecting the phase transition point of titanium alloy ingot, and therefore a more convenient and accurate detection method is needed to achieve better detection effect.

[0007] To solve the above problems, the present application adopts the following technical scheme: a titanium alloy ingot phase transition point detection method, comprising the following steps:

[0008] Step one, high temperature solid solution, a plurality of test samples are obtained by sampling from the ingot head, and all the test samples are heated to T β + (10-300) ℃, and then rapidly cooled after heat preservation;

[0009] Step two, low temperature aging, all the test samples cooled in step one are heat preserved at T β - (200-400) below, and then heated to T β - (30-60) ℃, and then cooled after heat preservation;

[0010] Step three, phase transition point detection heat treatment, all the test samples cooled in step two are divided into a plurality of groups, and the plurality of test samples are simultaneously heat treated, the number of heat treatment temperature values is equal to the number of test samples, and all the heat treatment temperature values are gradient distributed with T β as the center and equal difference;

[0011] Step four, phase transition point detection, the phase transition point is evaluated according to the high magnification organization content.

[0012] The principle of the scheme is: T β are empirical phase transition points, in step one, after the sample is solid-solved in the single-phase region and rapidly cooled, the sample structure becomes a supersaturated solid solution, and during the heating process after low-temperature aging in step two, due to the large free energy difference, the driving force for the nucleation of new phases is greatly increased, the interface of the new phase changes from a semi-coherent interface to a non-coherent interface with higher interface energy, and the alpha phase with a non-coherent interface will spontaneously recrystallize during the holding process at the phase transition point in step three, forming equiaxed or short rod-shaped alpha phases, so that the alpha phase can be clearly identified during the phase transition point detection in step four, and finally the phase transition point of the titanium alloy ingot can be conveniently and accurately detected.

[0013] The beneficial effects of the scheme are:

[0014] 1. High detection accuracy: Compared with the existing technology, which needs to obtain equiaxed or short rod-shaped alpha phases through multiple forging processes for better observation and identification, the process is more complex, and the internal structure of the titanium alloy will deteriorate during the multiple forging process, affecting the detection of the phase transition point of the titanium alloy ingot. In the present application, through specific high-temperature solid solution and low-temperature aging processes, the sample forms equiaxed or short rod-shaped alpha phases, effectively improving the display during the subsequent alpha phase detection process, which not only effectively reduces the detection difficulty, but also avoids the formation of lamellar alpha phases, and can clearly distinguish structures such as supercooled martensite, thereby improving the accuracy of phase transition point detection.

[0015] 2. Higher process feasibility: Compared with the detection method in the prior art, multiple forging processes are required during detection, which not only complicates the process, but also causes the internal structure of the titanium alloy to deteriorate during the multiple forging process, affecting the detection of the phase transition point of the titanium alloy ingot. The detection process in the present application does not require multiple forging processes to form easily identifiable equiaxed or short rod-shaped alpha phases, which not only improves the detection accuracy, but also simplifies the process and reduces the detection cost.

[0016] 3. Efficient detection: In the present application, the sample is treated by heat treatment process, which does not require a large amount of time for forging, and multiple samples can be treated simultaneously in steps one and two, thereby more efficiently completing the entire phase transition point detection.

[0017] 4. More accurate detection of the phase transition point of the titanium alloy: In the present application, the number of samples is multiple when setting the samples, and multiple temperature values equal to the number of samples are set in step three, all of which are distributed with a gradient difference of T β as the center, thereby more quickly and accurately detecting the phase transition point of the corresponding furnace batch of titanium alloy.

[0018] Preferably, as an improvement, in step two, T βThe holding time at the temperature of (200-400) degrees Celsius is 1-8 hours.

[0019] Preferably, as an improvement, the cooling mode in step two is air cooling. β The holding time after the temperature of (30-60) degrees Celsius is 60-600 minutes.

[0020] Preferably, as an improvement, the cooling mode in step two is air cooling.

[0021] Preferably, as an improvement, the holding time in step one is 10-200 minutes.

[0022] Preferably, as an improvement, the cooling mode in step one is water cooling.

[0023] Preferably, as an improvement, the difference between the adjacent heat treatment temperature values is 5 degrees Celsius.

[0024] Preferably, as an improvement, the holding time in step three is 30 minutes, and the cooling mode after the holding is water cooling.

[0025] In the scheme, when sampling at the ingot head position in step one, the sampling position is at the R / 2 position of the ingot head.

[0026] Preferably, as an improvement, the number of groups of the samples is 3-6, and the number of samples in each group is 5.

[0027] The beneficial effects of the scheme are:

[0028] 1. In step two, the temperature is increased to T β The holding for a long time at the temperature of 30-60 degrees Celsius and then gradually air cooling to room temperature make the interface of the new phase change from the semi-coherent interface to the incoherent interface with higher interface energy, and the alpha phase spontaneously recrystallizes to stably form the equiaxed or short rod-shaped alpha phase, and the whole process is controllable and stable.

[0029] 2. The cooling mode in step one is set to water cooling, so that the sample after high-temperature solid solution is rapidly cooled to form a supersaturated solid solution, greatly increasing the power of the alpha phase precipitation in step two and changing the morphology of the precipitated phase.

[0030] 3. In step three, the difference between the adjacent heat treatment temperature values is 5 degrees Celsius. According to the temperature change range of the phase transition point of different grades of titanium alloys, most of which are in the range of 20-40 degrees Celsius, the temperature difference between the adjacent heat treatment temperature values is set to 5 degrees Celsius, which can accurately and quickly detect the phase transition point temperature of the titanium alloy, the number of samples is moderate, and the temperature range can be conveniently and accurately controlled.

[0031] 4. The sampling position is located at the R / 2 position of the ingot head, and the microstructure of the sample is closer to the actual structure of the ingot, so that the sampling is more accurate, and the obtained data is more accurate.

[0032] 5. The sample is set to 3-6, and the temperature difference between adjacent heat treatment temperature values is 5℃, so that the whole sample can be tested in the range of 15-30℃, and T β is the empirical phase transition point, so as to ensure that the test is carried out in the range of 15-30℃ near T β , and the actual phase transition point of the ingot can be accurately detected; in addition, the number of samples in each group of samples is set to 5, and multiple samples are set at the same temperature, which can effectively reduce the detection error and make the detection result more accurate. BRIEF DESCRIPTION OF DRAWINGS

[0033] Fig. 1 is the high magnification microstructure of the sample in Example 1 at a heat treatment temperature value of 890℃ (the content of α phase is 10%).

[0034] Fig. 2 is the high magnification microstructure of the sample in Example 1 at a heat treatment temperature value of 895℃ (the content of α phase is 6%).

[0035] Fig. 3 is the high magnification microstructure of the sample in Example 1 at a heat treatment temperature value of 900℃ (the content of α phase is <1%).

[0036] Fig. 4 is the high magnification microstructure of the sample in the comparative example after multiple forging at a temperature value of 890℃ (the content of α phase is 14%).

[0037] Fig. 5 is the high magnification microstructure of the sample in the comparative example after multiple forging at a temperature value of 895℃ (the content of α phase is 4%).

[0038] Fig. 6 is the high magnification microstructure of the sample in the comparative example after multiple forging at a temperature value of 900℃ (the content of α phase is <1%). DETAILED DESCRIPTION

[0039] The following will be further described in detail through specific embodiments:

[0040] Example 1

[0041] This embodiment one: a titanium alloy ingot phase transition point detection method, comprising the following steps:

[0042] Step one, high temperature solid solution, get multiple groups of samples from the ingot head, the number of groups is preferably 3-6, and the number of samples in each group is 5, and the sampling position is at the R / 2 position of the ingot head, and after sampling, all samples are heated to T β + (10-300) ℃, and after holding, rapid cooling is performed, the holding time is 10-200 minutes, the rapid cooling method is water cooling, and the water cooling is to room temperature.

[0043] Step two, low temperature aging, all samples after water cooling to room temperature in step one are aged at T β - (200-400), the holding time is 1-8h, and then the samples are heated to T β - (30-60) ℃, and after holding, cooling is performed, the holding time is 60-600 minutes, and the cooling method is air cooling.

[0044] Step three, phase transition point detection heat treatment, all samples after cooling in step two are divided into multiple groups, and the multiple groups of samples are simultaneously subjected to heat treatment, the number of heat treatment temperature values is equal to the number of sample groups, all heat treatment temperature values are distributed in a gradient with T β as the center and a fixed temperature difference, in this embodiment, the temperature difference between adjacent heat treatment temperature values is 5℃, for example, the number of samples is five, and the number of heat treatment temperature values is also five, and the five temperature values are T β -10℃, T β -5℃, T β , T β +5℃, T β +10℃, so that different samples are treated at different heat treatment temperature values, wherein the heat treatment holding time is 30 minutes, and after heat treatment, water cooling is performed to room temperature.

[0045] Step four, phase transition point detection, evaluate the phase transition point according to the high magnification structure content.

[0046] Specifically, in this embodiment, a typical TC17 brand titanium alloy is taken as an example for illustration, the nominal composition of the TC17 titanium alloy is Ti-5Al-4Mo-4Cr-2Sn-2Zr, and the experienced average β transformation temperature is 895℃ (i.e. the value of T β , and the experimental steps are as follows:

[0047] Step one, high temperature solid solution, three groups of samples are obtained from the ingot head, the number of samples in each group is 5, and the sampling position is at the R / 2 position of the ingot head, the sampling size is 10*10mm, and after sampling, all samples are heated to 930℃ (i.e. T β +35℃), and after holding for 30 minutes, water cooling is performed.

[0048] Step 2: Low temperature aging: All the samples cooled to room temperature in step 1 are aging at 600℃ (T β -295℃) for 120 minutes, then the sample was heated to 850℃ (T β -45℃), keep warm for 120 minutes and then air cool.

[0049] Step 3: Phase transition point detection heat treatment: the three groups of samples cooled in step 2 are placed at three temperatures of 890°C, 895°C, and 900°C for heat treatment for 30 minutes, and then water-cooled.

[0050] Step 4: Phase transition point detection, check the high-magnification tissue content, and then evaluate the phase transition point based on the high-magnification tissue content. The test results are as follows: Figs. 1-3 shown.

[0051] Comparative Example: Three samples were taken from the ingot using the method of step 1. The three samples were tested according to the multi-fire forging method in the prior art. The temperatures of the multi-fire forging were 890°C, 895°C, and 900°C, which corresponded to the heat treatment temperature values ​​of the three samples in this embodiment. The test results are as follows: Figs. 4-6 shown.

[0052] according to Figs. 1-6 It can be seen from the comparison that when the sample is treated by the process method of this embodiment, the α phase obtained by the treatment of this embodiment is in the form of equiaxed or short rods when the phase transition point is detected. When the high-magnification tissue content is detected, it can be clearly and easily identified, and its size, morphology and Figs. 4-6 The microstructures obtained by medium and multi-fire forging are basically the same. Based on the α phase content of less than 3% as the basis for judging the phase transformation point, the final results of the two groups of tests are both 895~900℃, indicating that the phase transformation point determined by this technology is highly accurate and has high reliability in guiding subsequent forging processes.

[0053] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A method for detecting phase transition point of titanium alloy ingot, comprising the following steps: Step one, high temperature solid solution, take samples from the ingot head to obtain multiple groups of samples, heat all samples to T β + (10-300) °C, and then rapidly cool after holding Step two, low temperature aging, all samples after cooling in step one are aged at T β - holding in the range of (200-400) °C for 1-8 h, then increasing the temperature to T β - (30-60) °C, and then cooling after holding; Step three, phase transition point detection heat treatment, all samples after cooling in step two are divided into multiple groups, multiple groups of samples are simultaneously heat treated, the number of heat treatment temperature values is equal to the number of samples, all heat treatment temperature values are distributed in a gradient with T β as the center and a fixed temperature difference value. Step four, detecting phase transition point, evaluating phase transition point according to high-magnification structure content.

2. The titanium alloy ingot phase transformation point detection method according to claim 1, characterized in that: In step two, the temperature is raised to T β - the time for which the temperature is held after (30-60) °C is 60-600 minutes.

3. The method of claim 1, wherein the ingot is a titanium alloy ingot. The cooling mode in step two is air cooling.

4. The titanium alloy ingot phase transformation point detection method according to claim 1, characterized in that: The holding time in step one is 10-200 minutes.

5. The method of claim 1, wherein the ingot is a titanium alloy ingot. The cooling mode in step one is water cooling.

6. The method of claim 1, wherein: The difference between adjacent heat treatment temperature values is 5℃.

7. The method of claim 1, wherein the ingot is titanium alloy. The holding time in step three is 30 minutes, and the cooling mode after holding is water cooling.

8. The method of claim 1, wherein the ingot is a titanium alloy ingot. In step one, when sampling at the ingot head position, the sampling position is located at R / 2 position of the ingot head.

9. The method of claim 1-8, wherein the method is characterized by: The number of groups of the samples is 3-6, and the number of samples in each group is 5.

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